This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. ABSTRACT: SPIDER is an extensive image-processing software package specifically designed for 3D reconstruction in electron microscopy. It has been evolving in Dr. Frank's Lab since the late 1970's and contains appropriate tools for single particle reconstruction, classification analysis, and electron tomography, and segmentation of volumes. The current distribution consists of: + SPIDER Fast command line and procedural computation engine + Web Point-and-click GUI for image interaction + JWeb Point-and-click Java-based GUI for image interaction + SPIRE Point-and-click GUI for running SPIDER procedures + PubSub Scripted mechanism for distributing work on a compute cluster Since released as open source in 2005 there have been more than 1500 downloads of the software by recognizable registered users. SPIDER's web site is: http://www.wadsworth.org/spider_doc/spider/docs/spider.html.